Little-known Adeno-viruses May Be Key to Solving Unexplained Hepatitis in Children

Scientists in the United Kingdom have made a major breakthrough, saying they have found strong circumstantial evidence linking an obscure type of sidekick virus called adeno-associated virus to unexplained cases of hepatitis in children around the world.

The research also suggests that affected kids may share a genetic susceptibility, though it is not clear what role it plays in them having liver damage. Over 1,000 kids worldwide, more than 350 of them in the United States, have been diagnosed with hepatitis, or swelling of the liver, with no known cause, since October of last year, according to the World Health Organization (WHO).

Most of the children diagnosed with hepatitis are young, with the majority of the sick kids under the age of 5. Many of them were healthy before they suddenly got sick. At least 20 child patients in the United States have needed liver transplants, and 11 have died, according to the latest updates from the Centers for Disease Control and Prevention (CDC).

Scientists claim they have found the smoking gun in adeno-associated viruses

About half have tested positive for adenovirus 41, a stomach bug that commonly gives children diarrhea, vomiting, flu-like symptoms but has never been known to cause hepatitis before. Most of the kids who tested positive had low levels of adenovirus in their blood and no adenovirus infection in their livers, leading many doctors to suspect another cause such as COVID, or an environmental exposure or a complicating factor like genes.

Scientists said they may have found a smoking gun in adeno-associated virus 2, which is different from advenovirus 41, in two new studies. Adeno-associated virus 2 was present in high amounts in blood and liver tissue in nearly all the kids with unexplained hepatitis in the studies. And it was only rarely found in healthy children, those who had liver damage with a clear cause or those with only adenovirus infections but no liver damage.

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What is causing the hepatitis outbreak in children?

So what are adeno-associated viruses? They are tiny bits of DNA that can't copy themselves until they are in the presence of another virus, usually herpes or adenovirus. Adeno-associated viruses belong to a family of viruses called dependoparvoviruses.

According to virologists, they are kind of like remoras, the fish that attach themselves to sharks and eat the leftovers of their meals. Alex Greninger, who is the assistant director of the clinical virology laboratory at the University of Washington, said that a remora is not like the best analogy, but it is sort of like that. He added that it is got to have a host virus.

Gary Ketner, who is a molecular microbiologist at Johns Hopkins University, describes adeno-associated viruses as very small, DNA-containing viruses. He said they have just two genes. Given that they are by themselves when they infect cells, they are unable to grow because they don't encode all of the functions required for the replication. Ketner told CNN adeno-associated viruses depend on cells being infected at the same time with a helper virus, and the helper is usually adenovirus.

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